<!DOCTYPE html>
<html>
<head>
<!-- Without floats, no clearance applies, thus margin-top of #clear
     should collapse with margin-bottom of its parent element. -->
<style type="text/css">
#parent {
 margin-bottom: 10px;
}
.separator {
 height: 20px;
 background-color: green;
}
#clear {
 clear: left;
 margin-top: 20px;
}
</style>
</head>
<body>
<div id="parent">
 <div class="separator"></div>
 <div id="clear"></div>
</div>
<div class="separator"></div>
</body>
</html>
